1. Field of the Invention
The present invention relates to novel amorphous alloys with advantageous properties, such as very high corrosion resistance, high corrosion resistance at elevated temperatures and high wear resistance, which are useful in chemical plants or other industrial and domestic applications.
2. Description of the Prior Art
Generally, alloys are crystalline in the solid state. However, an amorphous structure, which is similar to a liquid but does not have a crystalline structure, is formed from specific alloy compositions by preventing the formation of long-range ordering of atomic arrangement during solidification through, for example, rapid solidification from the liquid state, sputter deposition using specific targets, etc. The alloys thus obtained are called amorphous alloys. The amorphous alloys are generally composed of a homogeneous supersaturated solid solution and have a significantly higher strength as compared with ordinary practical metallic materials. Also, the amorphous alloys have an extremely high corrosion resistance and other various advantageous properties depending on their compositions.
The present inventors have developed various amorphous alloys with a high corrosion resistance which have not been obtained in crystalline alloys. These amorphous alloys are roughly classified into two types, one being metal-semimetal amorphous alloys and the other metal-metal alloys. The metal-semimetal alloys consist of iron family elements of Fe, Ni and Co with semimetal elements, such as P, C, B or Si, in amounts of about 10 to 25 atomic % in which the semimetals are required to form an amorphous phase. The corrosion resistance of the metal-semimetal alloys have been enhanced by adding Cr thereto. On the other hand, the metal-metal system alloys consist of elements of Groups VIII and 1b, such as Fe, Co, Ni, Cu, etc., and valve metals of Groups 1Va and Va, such as Ta, Nb, Zr, Ti, etc. In the latter alloys, their corrosion resistance is provided due to the presence of the valve metals constituting the amorphous alloys. Particularly, among them, amorphous alloys including Ta or Nb of the Group Va provide an extremely high corrosion resistance.
As mentioned above, amorphous alloys including chromium, which is effective in improving the corrosion resistance properties of the amorphous alloys, require semimetals for amorphization. Further, metal-metal amorphous alloys have been obtained only from elements belonging to different groups which are listed apart from each other in the Periodic Table. In these two types of amorphous alloys, if single-phase Cr alloys with Ta and/or Nb can be obtained, such alloys can be expected as ideal alloys having an extremely high corrosion resistance because these elements improve the corrosion resistance of the alloys of the above-mentioned two different systems.
The present inventors have previously developed novel amorphous alloys and made various extensive studies on the properties thereof. As a result, it was found that amorphous alloys consisting of metals having high melting points and metals having low melting points can be prepared by using a sputter deposition process which does not require any melting step during the alloying process. In such a manner, the inventors have succeeded in preparing amorphous alloys consisting of an element or elements selected from Ti, Zr, Nb, Ta, Mo, W, etc., which belong to Group 1Va, Va or VIa, and an element or elements selected from Cu, Al, etc., which belong to Group Ib or IIIb. Some of the alloys thus obtained were filed in Japanese Patent Applications 62-103296, 63-51567, 63-51568, and 63-260020. Among those Japanese Patent Applications, the first three applications correspond to U.S. Pat. Nos. 5,030,300 and 5,041,175 and the forth application corresponds to U.S. Pat. Nos. 5,076,865 and 5,123,980.
The present inventor's studies were further continued and attempts were made to prepare high corrosion resistance metal-metal amorphous alloys from elements belonging to neighboring groups in the Periodic Table. As a result, amorphous alloys consisting of Ti and/or Zr belonging to Group 1Va elements and Cr belonging to Group V1a elements were successfully prepared and filed in Japanese Patent Application No. 3-138575.
The inventors further continued their studies and investigated alloying conditions, etc. They succeeded in preparing amorphous alloys from a combination of Nb and/or Ta selected from the group Va elements and Cr selected from the Group V1a elements. These Groups are neighboring groups in the Periodic Table and the selected elements, i.e., Nb, Ta and Cr are most effective in enhancing the corrosion resistance. The present invention was achieved on the basis of such a finding.